18650 Capacity Testing with B6AC

[codysmith105]

Hello EEVBlog community,

I'm getting into Lithium Ion cell recycling / reuse. This is basically pulling apart laptop battery packs and harvesting the 18650 cells for projects.

I bought an imax B6AC v2 charger and have started charging / discharging cells.

The first cell I put on the charger was already charged so I discharged it at 1A and I got 2096 mAh out of it (that's according to the charger and was a discharge from 4.1v to 3.1v).

I then charged the battery and only measured (again according to the charger) 1560 mAh.

These numbers are wildly different.

How can 2096 mAh go out and only 1560 go in?

Also, what procedure should I use to test cells with this charger / in general.

Thanks so much in advance guys.
-Cody